Always felt kind of scummy that the same guys maintaining this library - complete with frequent breaking changes - are selling training around React for 1.8k a pop.
In other industries, we call this a "conflict of interest". "Same guys writing the building code for 2017 (featuring many changes from the 2015 code) are selling in-person workshops on the 2017 building code!" Take it out of the context of software and it immediately feels dirty.